std::condition_variable::wait_for
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<metanoindex/>
<tbody> </tbody> template< class Rep, class Period > std::cv_status wait_for( std::unique_lock<std::mutex>& lock, const std::chrono::duration<Rep, Period>& rel_time); |
(1) | (desde C++11) |
template< class Rep, class Period, class Predicate > bool wait_for( std::unique_lock<std::mutex>& lock, const std::chrono::duration<Rep, Period>& rel_time, Predicate pred); |
(2) | (desde C++11) |
1)
Atomicamente libera
lock, bloqueia a thread atual em execução, e acrescenta-lo à lista de espera da thread em *this. A discussão será desbloqueado quando notify_all() ou notify_one() é executado, ou quando o tempo limite rel_time relativa expirar. Também pode ser desbloqueado spuriously. Quando desbloqueado, independentemente do motivo, lock é readquirido e sai wait_for(). Se esta função saídas via de exceção, lock também é readquirida.Original:
Atomically releases
lock, blocks the current executing thread, and adds it to the list of threads waiting on *this. The thread will be unblocked when notify_all() or notify_one() is executed, or when the relative timeout rel_time expires. It may also be unblocked spuriously. When unblocked, regardless of the reason, lock is reacquired and wait_for() exits. If this function exits via exception, lock is also reacquired.The text has been machine-translated via Google Translate.
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2)
Equivalente a
Original:
Equivalent to
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while (!pred()) if (wait_for(lock, rel_time) == std::cv_status::timeout) return pred(); return true;
Essa sobrecarga pode ser usada para ignorar despertares espúrios.
Original:
This overload may be used to ignore spurious awakenings.
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Parâmetros
| lock | - | um objeto de
std::unique_lock<std::mutex> tipo, que deve ser bloqueado pelo thread atualOriginal: an object of type std::unique_lock<std::mutex>, which must be locked by the current threadThe text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
| rel_time | - | um objeto de std::chrono::duration tipo que representa o tempo máximo de espera para gastar
Original: an object of type std::chrono::duration representing the maximum time to spend waiting The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
| pred | - | predicate which returns false se o tempo de espera deve ser continuado . Original: if the waiting should be continued The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. The signature of the predicate function should be equivalent to the following:
|
Valor de retorno
1)
std::cv_status::timeout se o tempo limite relativo especificado pelo
rel_time expirado, std::cv_status::no_timeout overwise.Original:
std::cv_status::timeout if the relative timeout specified by
rel_time expired, std::cv_status::no_timeout overwise.The text has been machine-translated via Google Translate.
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2)
false se o predicado pred ainda avalia a false após o tempo limite expirou rel_time, caso contrário true.Original:
false if the predicate pred still evaluates to false after the rel_time timeout expired, otherwise true.The text has been machine-translated via Google Translate.
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Exceções
Pode lançar std::system_error, também podem propagar exceções lançadas por
lock.lock() ou lock.unlock().Original:
May throw std::system_error, may also propagate exceptions thrown by
lock.lock() or lock.unlock().The text has been machine-translated via Google Translate.
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Notas
Chamar essa função se
lock.mutex() não está bloqueada pelo atual segmento é um comportamento indefinido.Original:
Calling this function if
lock.mutex() is not locked by the current thread is undefined behavior.The text has been machine-translated via Google Translate.
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Chamar essa função se
lock.mutex() não é o mesmo mutex como o utilizado por todos os outros segmentos que estão aguardando na variável mesma condição é um comportamento indefinido.Original:
Calling this function if
lock.mutex() is not the same mutex as the one used by all other threads that are currently waiting on the same condition variable is undefined behavior.The text has been machine-translated via Google Translate.
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Exemplo
#include <iostream>
#include <atomic>
#include <condition_variable>
#include <thread>
#include <chrono>
std::condition_variable cv;
std::mutex cv_m;
std::atomic<int> i = ATOMIC_VAR_INIT(0);
void waits(int idx)
{
std::unique_lock<std::mutex> lk(cv_m);
if(cv.wait_for(lk, std::chrono::milliseconds(idx*100), [](){return i == 1;}))
std::cerr << "Thread " << idx << " finished waiting. i == " << i << '\n';
else
std::cerr << "Thread " << idx << " timed out. i == " << i << '\n';
}
void signals()
{
std::this_thread::sleep_for(std::chrono::milliseconds(120));
std::cerr << "Notifying...\n";
cv.notify_all();
std::this_thread::sleep_for(std::chrono::milliseconds(100));
i = 1;
std::cerr << "Notifying again...\n";
cv.notify_all();
}
int main()
{
std::thread t1(waits, 1), t2(waits, 2), t3(waits, 3), t4(signals);
t1.join(); t2.join(), t3.join(), t4.join();
}
Saída:
Thread 1 timed out. i == 0
Notifying...
Thread 2 timed out. i == 0
Notifying again...
Thread 3 finished waiting. i == 1